Why does the GPS navigation on my car sometimes get stuck?

I think it's important for transit authorities, engineering societies, and ITS societies to confront the extreme vulnerability of GPS services to adversary attacks using simple, cheap jamming. Dodging the question is not helping anyone.

The strong asymmetry between widespread destructive impact and modest resources for a wide-ranging GPS jamming effort is extremely attractive to an adversary. Unlike hard terrorist attacks that involve violence with explosives, guns, and knives, widespread GPS jamming, while illegal, is non-violent but irritating to many people and organizations. An adversary operating a wide-range gps jammer on a congested, multi-lane highway could reap tempting rewards for destruction.